Part 37

The tribe of _Tenebrionidæ_, called formerly _Melasomas_, because they are nearly all black, resembles in some points the _Carabici_. They seek after dark places, and avoid the light, and are found on the ground under stones; their movements are slow, and they walk with difficulty. The best-known insect of this group is the _Blaps_, of repulsive smell, inhabiting dark damp places, such as cellars, and only coming out of its retreat during the night. The elytra are joined together, and they have no wings. The vulgar regard them as an omen of ill-luck. Fig. 541 represents the _Blaps obtusa_. According to the report of a traveller, the women in Egypt eat the _Blaps sulcata_ cooked with butter, to make them fat. They are employed also against the ear-ache, the bite of scorpions, &c.

Another genus of the same family is the _Tenebrio_ (Fig. 542), of a blackish-brown, with the elytra striated, and of half an inch in length. The larvæ, the well-known meal-worms, live in flour; they are cylindrical, and of a light tawny colour (Fig. 542). The insect which is considered as a type of the tribe of the _Pimelides_ is the _Pimelia bipunctata_, which is common in the south of France.

We come now to the tribe of blistering beetles, of which the best known is the Cantharides (_Cantharis_ or _Lytta_). These insects are generally of soft consistency, and their elytra very flexible. A few remain constantly on trees. All are very brisk and active. When swallowed they are a dangerous poison, but are used in medicine for making blisters.

The Cantharides of commerce (_Cantharis_ [_Lytta_] _vesicatoria_) are of a beautiful green, attain to a size of four-fifths of an inch, and are found on ash-trees, lilacs, and other shrubs. Commerce for a long time brought them from Spain, and some still come from that country; hence the common name of _Spanish fly_. As they live in great numbers together, collecting them is easier and less expensive than would be that of other species of the same family which are not gregarious, but which have the same medicinal properties. The presence of the Cantharides is manifested by the strong penetrating odour which they diffuse to some distance. When, by aid of this smell, they are discovered, generally settled on an ash, they are collected in the following manner:--Very early in the morning a cloth of light tissue is stretched out at the foot of the tree, and the branches are shaken, which causes the insects to fall (PLATE XII.). These, numbed by the cold of the night, do not try to escape. When there is a sufficient quantity, the four corners are drawn up and the whole plunged into a tub of vinegar diluted with water. This immersion causes the death of the insects. They then carry them to a loft, or under a very airy shed. To dry them they spread them out on hurdles covered with linen or paper, and from time to time, to facilitate the operation, they are moved about, either with a stick or with the hand, which is more convenient; but it is then necessary to take the precaution of putting on gloves, for, if touched with the naked hand, they would cause more or less serious blisters. The same precaution must be observed in gathering them.

When the Cantharides are quite dry, they put them into wooden boxes or vessels of glass or earthenware hermetically sealed, and preserve them in a place protected from damp. With these precautions, they may be kept for a long while without losing any of their caustic properties. Dumeril made blisters of Cantharides which had been twenty-four years in store, and which had lost none of their energy. When dry, they are so light that a kilogramme contains nearly 13,000 insects. Aretius, a physician who flourished at Rome in the first century of our era, seems to have been the first to employ Cantharides, reduced to powder, as a means of vesication. Hippocrates administered them internally in cases of dropsy, apoplexy, and jaundice. But it is pretty nearly established that the Cantharides of the ancients were not the same species used at the present day; they were, probably, a kindred species, the _Mylabris chicorii_. A blistering principle has been extracted from these insects, called _Cantharadine_. This organic product presents itself under the form of little shining flakes, without colour, soluble in ether or oil. One atom of this matter applied to the skin, and particularly to the lower lip, makes the epidermis rise instantaneously, and produces a small blister filled with a watery liquid. In spite of the corrosive principle which the _Cantharis_ contains, it is attacked, like other dried insects, by the _Dermestes_ and the _Anthrenus_, which feast on them without suffering the smallest inconvenience.

The _Stylopidæ_, for which Kirby,[122] in 1811, instituted a distinct Order, which he called _Strepsiptera_, in allusion to the contortion of the elytra, and to which Latreille[123] subsequently applied the name of _Rhipiptera_, are, perhaps, the most anomalous of all insects. Great diversity of opinion has existed respecting their affinities; but modern systematists, with but few exceptions, concur in referring them to the Order _Coleoptera_, and locating them in proximity to _Meloë_. In the larva state, all the known species of the family inhabit the bodies of hymenopterous insects of the genera _Andrena_, _Polistes_, &c., in this particular resembling the dipterous genus _Conops_, which inhabits the body of humble bees,[124] and apparently in no way inconveniencing their victims; a fact which has been accounted for on the supposition that their existence in the larva state is but short, and that their attacks being directed against the abdomen, and not the thorax, the seat of life in insects, their presence does not affect the activity of the victim. The larva has a soft fusiform body, surmounted by a somewhat globose head. While feeding, the head is towards the base of the abdomen; but on changing to a pupa, this position is reversed, and the head--at first of light brown, but which after a short time becomes black--thrust out between the plates of the abdomen.

[122] "On a new Order of Insects," _Linn. Trans._, vol. xi.

[123] In Cuvier, "Le Règne Animal," ed. i., tome iii., p. 584.

[124] See p. 69.

The imagos, which are of small size, namely, about the eighth of an inch long, are found during May and June. They have four wings, but the anterior pair, of hard texture, somewhat resembling elytra, but hardly answering to them in structure, are very poorly developed, and curled round the front pair of legs, hence the name bestowed, by Kirby, from [Greek: strepssis], a twisting, and [Greek: pteron], a wing; the posterior wings are fully developed, and fold up like a fan, whence the Order received the name of _Rhipiptera_ from Latreille. The eyes, the facettes of which are few in number, are placed on a footstalk, whence the name of the genus _Stylops_. The parts of the mouth connect the Strepsiptera with the mandibulated insects, although by some supposed to bear analogy by their functions to those parts in the Diptera. The male only is winged; the female is very like an apodal larva, the larva being an active hexapod.

The family _Stylopidæ_ is divided into four genera, of which two only, _Xenos_ and _Stylops_, were described by Kirby in the essay referred to above. First, _Xenos_, from [Greek: xenos], a guest, the most prolific in species, of which _Xenos Rossii_, sometimes called _vesparum_, may be taken as the type. Secondly, _Elenchus_, of which _Elenchus Walkeri_ is the type. Thirdly, _Stylops_ (Fig. 543), parasitical on various species of _Andrenæ_, of which _Stylops Melittæ_, having a fleshy abdomen and the wings longer than the body, may be considered typical: and lastly, _Halictophagus_, of which only one species, infesting _Halictus æratus_[125] named _Halictophagus Curtisii_, is known to exist, and which makes its appearance in the month of August.

[125] _Halictus_ and _Andrena_ are two genera of Bees.

These singular insects are found in various parts of the world--Europe, Australia, and America. They were discovered by Professor Peck almost simultaneously with Mr. Kirby's discovery in this country, and to whom he sent specimens of a species which has received the name of _Xenos Peckii_ lately, in New Zealand and elsewhere.

Siebold, in 1843, having obtained some eggs, was able to observe the larvæ, and he soon discovered that the females of Stylops, one of the Strepsiptera, were blind, had no legs, and always retained the appearance of larvæ, and that they never quitted the bodies of those insects, in which they pass a parasitic existence. George Newport paid great attention to the history of these curious insects, and when he wrote his article, "Insecta," in the "Cyclopædia of Anatomy and Physiology," four distinct genera of these minute parasites had already been discovered. One of the largest species (_Stylops Spencii_) is scarcely more than two lines in length, while the smallest species yet known is not more than two-thirds of a line, or scarcely a line in breadth with its wings expanded. They undergo metamorphosis; and the males, when they have become perfect insects, fly and roam about, but the females are condemned to a perfectly quiet life. The head and the thoracic segments of the bodies of these last are united completely, but the abdomen, which is very large, always remains soft, so that the whole of the body only appears to be formed of two portions. They are ovo-viviparous insects, and the young larvæ escape as such from the body of the mother. They are active creatures, and, being furnished with long legs, crawl over the hairs and skin of the hymenopterous insect they are parasitic upon. They behave like the larvæ of Meloë and Sitaris, whose peculiar methods of life have been noticed in our description of the Coleoptera. Clinging on to a wasp or a bee, they are carried off, and finally arrive in the nest or hive, as the case may be, and there they attack the larvæ. When once fixed upon the hymenopterous larvæ, they undergo a change of skin, and their shape then becomes totally different, and their legs are atrophied. But these parasites being exceedingly small, do not kill the larvæ; they suck their juices, after the manner of the Ichneumons, and do not interfere with the metamorphoses of the insects upon which they are parasitic. On the right hand, in the accompanying engraving (Fig. 544), there is a larva much magnified, lately born, and climbing upon the hair of one of the Hymenoptera, and on the left hand there is a perfect female insect, very much magnified, with ovo-viviparous larvæ within its abdomen, and between the two figures there is a representation of a larva of the natural size. It is evident, however, that ova may be expelled from the mother before they are hatched.

Packard describes the curious history of the female Stylops, which he found parasitic on one of the bees. He caught the bee, and on examining it he noticed a pale reddish-brown triangular mark on the abdomen, and this was the flattened head and thorax of a female Stylops. The creature is included in the body of the bee, and is nourished by its juices. The head and thorax of the parasite were noticed to be soldered into a single flattened mass, the baggy hind body being greatly enlarged, like that of the female white ant. On carefully drawing out the whole body from the bee the mass was found to be very extensible, soft, and baggy, and on examining it under a high power of the microscope, multitudes of very minute larvæ were observed, and they began to issue out from the body of the parent all alive, and not as eggs. The male of this _Stylops childreni_ is totally unlike its partner, having large hind wings, and being able to fly, as has already been noticed. It appears, then, that the larvæ are hatched or crawl out of the body of the mother on to the body of the bee, and are then transported to its nest; then they enter the body of the bee larva, and live upon its fatty matter. The male Stylops is turned into a pupa within the bee, and so is the female; but after the second metamorphosis the male flies off, leaving his wingless partner imprisoned for life, and she usually dies immediately after giving birth to her myriad offspring (Packard). The female respires by peculiarly arranged tracheæ, and absorbs nourishment through her skin as well as by means of an alimentary canal, which ends in a blind sac. All the beauties of the female, so far as they are visible to the male, consist in the tiny patch which appears just without the body of the unfortunate bee, and the ova collect in a space which opens between the united head and body and the abdomen.

The genus _Mylabris_ corresponds most in structure, in appearance, and in properties, to _Cantharis_, whose place they take in the East, in China, and in the south of Europe. They are found in clusters on the flowers of chicory, thistles, &c. The _Mylabris chicorii_, common enough in France, especially in the south, is of small size, whilst the other species are rather large. It is black, hairy, with a large yellowish spot at the base of each elytron, and two transverse bands of the same colour.

Another genus of this family is _Meloë_, with very short elytra, and without wings. They walk slowly and with difficulty on low plants, the female dragging along an enormous abdomen filled with eggs. They are generally observed in spring. In Germany they give them the name of _Maiwurm_ (Mayworm). Their succulence would expose them, without doubt, to the voracity of birds and of insect-eating Mammifers if they had not the power of exuding at will, in the moment of danger, from all their articulations, an unctuous humour of a reddish-yellow colour, the odour and probably also the caustic properties of which repel the aggressor. The females lay their eggs underground, and out of these come forth larvæ of a strange shape. Swallowed by cattle, they cause them to swell and die. It is for this reason that Latreille has given it as his opinion that these insects are the _Buprestis_ of the ancients, of which the law of Cornelius speaks, "Lex Cornelia de sicariis et veneficis." But the name of _Buprestis_ was applied by Linnæus to a genus of which we shall treat farther on, and it has been generally adopted by naturalists.

The commonest among the _Meloës_ is the _Meloë proscarabæus_, which is to be found in abundance, in the month of April, in the meadows near the bridge of Ivry in the environs of Paris. The metamorphoses of the insects of this family had remained for a long time surrounded with an impenetrable veil of mystery, but the researches of Newport in England, and of M. Fabre (of Avignon) in France, has made known in our days, phases, extremely curious, under which are accomplished the metamorphoses of the _Meloë cicatricosus_, and of the _Sitaris humeralis_, a species which belongs to the same family.[126] These observations, of which we are about to give a rapid summary, will probably help towards unravelling the first states of _Cantharis_.

[126] "Annales des Sciences Naturelles," 1857, 4e série, tome vii., p. 300.

The _Sitaris humeralis_ (Fig. 545) takes no nourishment when arrived at the perfect state. When the female has been impregnated, she lays at the entrance of the nest of a solitary bee from 2,000 to 3,000 small whitish eggs, stuck together in shapeless masses. A month afterwards there come out of these eggs very small larvæ, of a shiny dark green, hard-skinned, armed with strong jaws, and long legs and antennæ (Fig. 546). These are the first larvæ. They remain motionless, and without taking food, till the following spring. At this period are hatched the male bees, which precede the appearance of the females by a month. As the bees come out of their nests, these larvæ hook themselves on to their hairs, and pass them to the females, at the coupling period. When the male bees have built the cells, and furnished them with honey, the female, as we know, deposits in each an egg. Immediately the larvæ of the _Sitaris_ let themselves fall on these eggs, open them, and suck their contents. Then they change their skin, and the second larva appears. This one gets into the honey, on which it feeds for six weeks. It is blind, whereas the first larva was provided with four eyes, no doubt to enable it to see the bees which were to serve as its conductors, in like manner as the companions of Ulysses watched the sheep of Polyphemus, so as to escape out of the cave in which they were retained as prisoners. A few days later, and this second larva contracts, and detaches from its body a transparent skin, which discloses a mass, at first soft, which very soon hardens, and becomes of a bright tawny colour; it is called the _pseudo-nymph_ (Fig. 547). It goes through the winter in this state. In the spring comes forth a third larva (Fig. 548), resembling the second. This one does not eat, and moults after a time. It very soon changes into an ordinary pupa (Fig. 549), of a yellowish-white, from which comes forth the adult _Sitaris_, which lives only a few days, to ensure the propagation of its species, as is observed in the case of the _Ephemeræ_. The larvæ of the _Sitaris_ had for a long time been remarked clinging on to the hairs of the _Anthophoras_, but they were always taken for _Acari_, and they had been described as such.

The _Lampyridæ_ have the elytra weak and soft, like the insects of the preceding tribe. In their perfect state they frequent flowers. The larvæ are carnivorous, attacking other insects or worms. It is to this group that the _Lampyris noctiluca_, or glow-worm, which one sees shining during summer nights on grass and bushes, belongs. It has the power of making this natural torch shine or disappear at will.

The luminous properties with which these insects are endowed have for their object to reveal their presence to the opposite sex, for the females alone possess these properties. In the same way as sounds or odours exhaling from some insects attract the one towards the other sex, so with the _Lampyris_ a phosphorescent light shows the females to the males. The seat of the phosphorescent substance varies according to the species. It exists generally under the three last rings of the abdomen, and the light is produced by the slow combustion of a peculiar secretion. It has been stated that it is evolved quickly when the animal contracts its muscles, either spontaneously or under the influence of artificial excitement. Some chemical experiments have been made to ascertain the nature or the composition of the humour which produces this strange effect; but up to this moment, they have only enabled us to discover that the luminous action is more powerful in oxygen, and ceases in gases incapable of supporting combustion. In the most common species, the _Lampyris noctiluca_, or glow-worm, the phosphorescence is of a greenish tint: it assumes at certain moments the brightness of white-hot coal.

The females have no wings, while the males have them, and possess very well-developed elytra. The females resemble the larvæ much, only they have the head more conspicuous, and the thorax buckler-shaped, like the male. The larvæ feed on small molluscs, hiding in the snails' shells, after having devoured the inhabitant. They also possess the phosphorescent property in a less degree than the adult females. The female pupa resembles the larva; the pupa of the male, on the contrary, has the wings folded back under a thin skin. The perfect insect appears towards the autumn.

The Glow-worm (_Lampyris noctiluca_, Fig. 550) is of a brownish yellow. It is common in England. In a kindred species, the _Luciola Italica_, the two sexes are winged, of a tawny-brown, and equally phosphorescent. They are met with in great numbers in Italy, and the lawns are covered with them. Other insects of this family are without the faculty of emitting light; as, for example, the genus _Lycus_, of brilliant colours, which are met with in Africa and India. One of the finest is the _Lycus latissimus_.

_Drilus_ is another genus, comprising insects of very singular habits. The type is the _Drilus flavescens_. The male--a quarter of an inch long, black and hairy, with elytra of a testaceous yellow, and with pectinated antennæ--for a long time was alone known. The female--from ten to fifteen times as large, without wings and elytra, of a yellowish brown--was not discovered till much later, having apparently nothing in common with the male in shape or colour. The metamorphoses of these curious insects are now perfectly understood. Mielzinsky, a Polish naturalist established at Geneva, found the _Drilus_ in the larva state in the shell of the _Helix nemoralis_. These larvæ devour the snail whose dwelling they occupy, as do the larvæ of the _Lampyris_. Mielzinsky saw them emerge, but obtained only females, which differed scarcely at all from the larvæ from which they proceeded. He made a separate genus of them, under the denomination of _Cochleoctonus_, and called the species _Vorax_. Later, Desmarest resumed these observations. He provided himself, at the Veterinary College of Alfort, with a number of shells of the _Helix_ filled with the same larvæ. He saw come out of them, not only _Cochleoctoni_, but also _Drili_, and he watched their coupling. It was then proved, by this unanswerable argument, that these two insects, so unlike each other, belong to the same species.